Clutch spring



Feb. 11, 1936. w. c. STARKEY' 2,030,333

CLUTCH SPRING Original Filed Jan. 7, 1951 Patented Teb. 11, 1936 UNITEDSTATES 2,030,333 oLU'rcn SPRING William C. Starkey, Indianapolis, Ind.,assignor,

by mesne assignments, to William C. Starkey, Indianapolis, Ind., RaymondS. Pruitt and Walter H. Beal, Chicago,

Ill., trustees Original application January 7, 1931, Serial No.

Divided and this application March 21, 1932, Serial No. 600,139

Claims.

This invention relates to improvements in clutch springs, and itconsists of the matters hereinafter described and more particularlypointed out in the appended claims.

' The present-application is a. divisional one, as the subject matterherein was first presented in my copending application, Serial Number507,062, filed January 7th, 1931 (now Patent No. 1,953,370, dated April3, 1934.)

The spring embodying my invention is of especial advantage in that typeof clutch embodying two coaxial, cup-shaped members, adapted to receivea helical spring, which in response to relative rotation of said membersin one direction,

freely permits such rotation but which in response to rotation of saidmembers in the other direction acts to clutch said members together forconjoint rotation.

The primary object of the invention is to provide a spring for use in aclutch of this kind, wherein the end turns or coils at the unanchoredend of the spring assume only a small percentage of the load to be heldand each consecutive turn or coil toward the middle of the springassumes a successively greater percentage of saidlead until that turn orcoil is reached which crosses the planeoi the meeting ends of thecup-shaped members and which turn or coil assumes the entire load. vAnother object of the invention is to provide a spring for the purposementioned which is easy to make and although it is made of stock of thesame cross sectional area throughout its length, is rendered moreflexible at one end by the provision of a plurality of axially extendinggradient grooves in several of the turns or coils at said end of thespring.

The above mentioned objects of the invention as well as others, togetherwith the many advantages thereof, will more fully appear as I proceedwith my specification.

In the drawing:

Fig. 1 is a longitudinal vertical sectional view through a spring clutchembodying the preferred form of spring made in accordance with myinvention.

Fig. 2 is a perspective view of the preferred form of clutchspringembodying my invention.

Fig. 3 is a view in side elevation of a slightly modified form of clutchspring embodying my invention.

Fig. 4 is a. fragmentary longitudinal sectional view through a modifiedform of spring clutch in which my improved clutch spring is readilyusable.

The improved clutch spring is herein illustrated and will be hereindescribed, as embodied in the pinion unit of an engine starter but thisis to be considered as illustrative only, of one of the many uses forsuch a spring, because as will be apparent, the improved spring may alsobe used in clutches for other purposes when the peculiar characteristicsof the spring make it of advantage to do so.

In general, the improved spring is wound in the usual manner from alength of spring stock having the same cross sectional area throughoutits entire length and one end of said length of stock is bent axially toprovide a toe at one end of the spring while the other end of the springis ground fiat. The spring is thereafter ground face for the, spring.Preferably before such grinding is performed, a plurality of arcuatelyspaced, longitudinally extending gradient grooves are produced in thatend of the spring opposite its toed'end with the deepest end of thegrooves at the extremity of the spring. Thus the turn at said end of thespring is the most flexible and this flexibility decreases in thesuccessive turns or coils until that turn or c'oil, having theshallowest end of the grooves, is reached.

Referring now in detail to that embodiment of the invention, illustratedin Figs. 1 and 2 of the accompanying drawing:-| indicates as a whole thedriven shaft of an automobile or like engine starting motor, having asplined part 2 of enlarged diameterat that end remote from said motor. IOn said shaft is mounted a bearing sleeve or bushing 3. A cupshapedclutch member 4 is provided at one end with a hub 5 having a splinedconnection with the like part 2 of the shaft I.

A second clutch member 6 has a hub l at one end that is journalled onthe sleeve 3 and is held against endwise movement in one directionthereon by a spring retaining ring 8 suitably en gaged in an annulargroove in said sleeve. On said hub is formed the pinion 9 which in an'endwise movement of both cup-shaped members toward the starting motoris adapted tobe moved into engagement with the fly wheel ring gear (notshown) of the engine to be started.

Both cup-shaped members are formed at their abutting ends to provide aclutch spring recess 10 having flat ends it and. i2 respectively and anannular clutch surface 13.

In said recess is located. a clutch spring I4 embodying the preferredform of my invention.

' Said spring is of an external diameter when in its normal unstressedcondition, approximating peripherally to provide the desired grippingsur-' that of the surface I3. Thatturn or coil of the spring associatedwith the end H of the recess is turned axially to form a, toe l5 adaptedfor engagement in a pocket l6 formed in the member 4 and opening throughthe fiat end of said recess. Preferably this turn or coil of the springis also provided with one or more axially exing the shallowest end ofthe tending studs i1 adapted for contact against the surface of the flatend I I to squarely support the end of said spring.

That turn or coil I 9 at the other end of the spring is ground flat forengagement with'the end I2 of the recess and is devoid of any toe orstuds such as are. associated with the first mentioned end of thespring.

In the second mentioned end of the spring which is in fact theenergizing end thereof, I provide in one surface of the spring, aplurality of longitudinally or axially extending gradient grooves 20.Said grooves are deepest at that end opening through the turn or coil I9and gradually decrease in depth toward the middle turn or coil of thespring. Preferably these grooves terminate short of the plane of themeeting ends of the two cup-shaped members 4 and 6 as best shown in Fig.1 and preferably these grooves are in the external surface of the springbecause of the ease in which they can there be produced.

As shown herein, I provide six of such grooves. spaced equal arcuatedistances apart. Thus with such a spring, the endmost turn or coil I 9is relatively speaking, the most flexible one of the spring and thisflexibility decreases in the successive turns or coils until that turnor coil havgrooves therein is reached.

As said grooves become more and more shallow the various turns retaingreater percentage of their total rigid strength until where the groovesrun out 01' disappear, the turns or coils retain their full strength andrigidity.

During relative rotation of the ,cup members 4 and 6 in one'direction,as when the member 4 is being driven by the shaft l in the properdirection, said member will through the toe J5 tend to turn the springin a direction to unwind the same. i

As the opposite end of the spring is the mostflexible one because of thearrangement of the grooves as before described, it is apparent that Ithe turn or coil at said end will be the first one to be efiectedthereby and radially expand and then the nextone and so on until all ofthose turns or coils having portions of the grooves therein will be.expanded into engagement with that part of the surface l3 near said endl2. Thus the turn or coil I9 will assume only a small part or percentageof the total load and each successive turn or coil will assume asuccessively greater part of the load until that coil is reached whichcrosses the plane of the meeting ends'of the cup-members wherein saidtotal load is assumed.

Thus in the spring structure mentioned the slots have in no mannerdecreased the total load value of the spring because the end turn orcoll l9 from a. standpoint of proper functioning would not need a crosssectional area such as in that turn which crosses said'plane of themeeting ends of the cup members to retain the full capacity of thespring.

Again, thisend of the spring with its flexi-' bility has anotheradvantage in that only a light overrun or frictional drag is had andthiswould still be true even though the end turn or coil be characteristicsdesired. In Fig. 3 is shown a spring wherein the endmost turn or coill9a is I several thousandths of an inch larger than those at the otherend which are made of a diameter approximating that of the recess. Thusthe endmost turn or coil l9a may be .015" greater than that of therecess in-which it is used, the next turn being .010" over recess sizeand the third turn or coil being .005" over recess size. I

This relative" diameter of the turns or coils at the unanchored end of'the spring with respect to the recess'diameter may be secured in twodifferent ways. I In the case of the spring shown in Fig. 3, these turnsor coils at the unanchored end may be made by actually expanding themsimply by driving a taper mandrel 2| thereinto until these turns orcoilstake on a permanent set.

Again, the same result may be obtained by leaving the spring perfectlycylindrical on its external surface and by tapering one end of therecess as at Ilia in Fig. 4.

In grinding flat that end of the spring shown in Figs. 1 and 2,embodying the turn l9, said turn presents but a narrow contact surfacefor engagement with the cylindrical wall of the recess near theassociated end which insures cutting through the lubricant film on theend surface I2 of the recess to make a better metal-to-metal contactbetween said end turn or coil and said locking effort.

As is shown in Fig. 2, similar slots 22 may be formed in the anchoredend of the spring and these slots terminate short of the turn that wouldcross the plane of the meeting ends of the cup members 4 and 6; Theseslots are disposed in the external surface of the spring, in planesbetween those of the slots 20 and at their deepest part would be onlyabout one half the depth. of said slots 20 and would taper out tonothing at their other ends.

This would cause the anchored end turn or coil to be slightly moreresilient but would not detract from its compression strength and wouldinsure its coming into positive intimate contact with the end of therecess so that these three or more or coils are made of substantiallylarge cross sectional stock, is changed to one of the desiredflexibility for the intended purpose.

Heretofore, in a spring without such a flexible end, it was notpractical to have the same more than .003" or .004" over that of thediameter of that part of the recess engaged thereby in the case ofoverrunning clutches because of great overrun friction. On the otherhand, with this wound and ground in the usual manner after which it isgrooved'exteriorly as shown. I

While in describing the invention, I have referred in detail to theform, arrangement and .of the spring.

other end of the spring and .to r

construction of the parts thereof, the same is to be consideredas-illustrative only, so that I do not wish to be limited thereto exceptas maybe specifically set forth in the appended claims.

I claim as my inventionz I 1. As a new article of manufacture, a clutchspring embodylng'a'plurality of coils-and having one of the peripheriesthereof ground to form clutching surface certaln of the coils beingaxially-grooved in the portions thereof which form the clutching surfacein orderto make them more flexible than the other coils of the springand to receive lubricant removed from the surface with which saidclutching surface is adapted to coact in response to. a change in thediameter 2. As a; new" manufacturaa clutch spring embodying apluralityof'coils and havin one of the peripheries thereof ground toform a clutching surfacdtheboils atone end of .saidspring being axiallygrooved in the portions thereof which define saidclutching surface inorder a to make them more flexible than he coils at the removed from thesurface -.with which said clutching surface is adapted to coact inresponse to a change in diameter of the spring. I

3. As a new article of manufacture, a clutch spring embodying aplurality of abutting coils of the same cross sectional area and havingone of the peripheries thereof ground to form a clutching surface,certain of the coils being axially grooved in the portions thereof whichdeflne said clutching surface in order to make'them more flexible thanother coils of the sprlngand to receivelubricant removed from thesurface with which said clutching surface is adapted .to coact inresponse to a change in the diameter of the spring. s

.4. As a new article of manufacture, a clutch spring embodying aplurality of coils of the same cross sectional area and having the outerperiphery thereof ground to form a clutching surface, the coils at oneend of said spring being axially grooved in the portions thereof whichdefine said clutching surface in order to make them more flexible thanthe coils at the other end of the spring and to receive lubricantremoved from the surface with which said clutching surface is adaptedtocoact in response to expension of the spring.

eive lubricant 5. As a new article of manufacture, a clutchspring'embodying a plurality of abutting coils and having one of theperipheries thereof ground to form a clutching surface, the end coil atone end of the spring being formed to provide anchorage means for thespring and the end coil at the other end of the spring being ground flatand having together with the other coils at said other end of the springaxially extendinggrooves in the surfaces thereof which define theclutching surface in order to increase the flexibility thereof over thecoils at said one end'of the spring, and to receive lubricant removedfrom the surface with which said clutching surface is adapted to coactin response to a change in the diameter of the spring.

6. As a new article of manufacture, a clutch spring embodying aplurality of coils and having the outer periphery thereof ground to forma cylindrical clutching surface, the coils at one end of the springbeing provided in the outer portions thereof with axially-extendinggrooves which decrease in depth from the outer to the inner ends thereofand serve to render the coils in which they are formed more flexiblethan the other coils of the spring and to receive lubricant removed fromthe surface with which said clutching surface is adapted to coact inresponse to expansion of' the spring. 1

7-. As a new article of manufacture, a clutch spring embodying aplurality of abutting coils and having one of the peripheries thereofground to form a substantially cylindrical clutch surface,

t which the clutching surface is adapted to coact in response to achange indiameter of. the spring. 8. Asa new'article of manufacture, aclutch spring embodying a plurality of abutting coils of uniformdiameter and the same cross 'sectional area having the outer peripherythereof ground to form a cylindrical clutchingsurface, the coils at oneend of, the spring having axially extending grooves in the outerportions thereof which taper and decrease in depth from the outer to theinner ends thereof and operate to make the coils in which they areformed more flexible than theother coils of the spring and to receivelubricant removed from the surface with which the clutching surface isadapted to coact in response to expansion of the spring. I

9. A clutch spring embodying therein a plurality of coils made of stockof the same cross sectional area, said spring having a groundcylindrical gripping surface, certain of the coils having axiallyextending radient grooves in. said gripping surface to make said certaincoils more flexible than the other coils of the spring.

10. A clutch spring embodying therein a plurality of coils made of stockof the same cross sectional area, said spring having a ground external,cylindrical gripping surface, certain of the coils at an end of thespring having axially extending gradient grooves in one end of saidgripping surface to make said certain coils more flexible than the othercoils of the spring.

WILLIAM C. STARKEY.

